export function shuffle(source) {
    const arr = source.slice()
    for (let i = 0; i < arr.length; i++) {
      const j = getRandomInt(i)
      swap(arr, i, j)
    }
    return arr
  }

  function getRandomInt(max) {
    return Math.floor(Math.random() * (max + 1))
  }

  function swap(arr, i, j) {
    const t = arr[i]
    arr[i] = arr[j]
    arr[j] = t
  }

  export function formatTime(interval) {
    interval = interval | 0
    const minute = ((interval / 60 | 0) + '').padStart(2, '0')
    const second = (interval % 60 + '').padStart(2, '0')
    return `${minute}:${second}`
  }
